2LiBH(4)-MgH2 nanoconfined into carbon aerogel scaffold impregnated with ZrCl4 for reversible hydrogen storage

Nanoconfinement of 2LiBH(4)-MgH2 composite into carbon aerogel scaffold (CAS) impregnated with zirconium (IV) chloride (ZrCl4) for reversible hydrogen storage is proposed. Nanoconfined samples prepared with hydride:ZrCl4-doped CAS weight ratios of 1:1, 1:2, and 1:3 are prepared by melt infiltration technique. Successful nanoconfinement of all samples is confirmed and it is found that the sample with high content of hydride with respect to ZrCl4-doped CAS (1:1 weight ratio) shows partial pore blocking. The most suitable hydride:ZrCl4-doped CAS weight ratio providing the best performance based on dehydrogenation temperature and kinetics as well as hydrogen storage capacity is 1:2. Reduction of dehydrogenation temperature and faster kinetics are obtained after doping with ZrCl4. Up to 97 and 93% of theoretical hydrogen storage capacity are released and reproduced after four cycles of nanoconfined sample with ZrCl4 (1:2 weight ratio). Deficient hydrogen content with respect to theoretical capacity can be due to partial dehydrogenation during melt infiltration and formation of thermally stable [B12H12](2-) phases during cycling

Hydrogen sorption kinetics, hydrogen permeability, and thermal properties of compacted 2LiBH4-MgH2 doped with activated carbon nanofibers

To improve the packing efficiency in tank scale, hydrides have been compacted into pellet form; however, poor hydrogen permeability through the pellets results in sluggish kinetics. In this work, the hydrogen sorption properties of compacted 2LiBH4MgH2 doped with 30 wt % activated carbon nanofibers (ACNF) are investigated. After doping with ACNF, onset dehydrogenation temperature of compacted 2LiBH4MgH2 decreases from 350 to 300 °C and hydrogen released content enhances from 55 to 87% of the theoretical capacity. The sample containing ACNF releases hydrogen following a two-step mechanism with reversible hydrogen storage capacities up to 4.5 wt % H2 and 41.8 gH2/L, whereas the sample without ACNF shows a single-step decomposition mainly from MgH2 with only 1.8 wt % H2 and 15.4 gH2/L. Significant kinetic improvement observed in the doped system is due to the enhancement of both hydrogen permeability and heat transfer through the pellet